Applicant is a co-inventor under U.S. Pat. No. 4,821,509 issued on Apr. 18, 1989, for "Pulsed Electrothermal Thruster". This application relates to significant improvements in the apparatus and methods disclosed in the cited patent, which is the closest prior art known to applicant.
U.S. Pat. No. 4,821,509 includes a section entitled "Background Art" which discusses several prior patents and applications, may be of some interest to a worker in this field, and is incorporated herein by reference.
In summary, the prior patents and applications discussed in U.S. Pat. No. 4,821,509 all relate to the use of directed plasmas to accelerate or propel masses attached to the thruster which creates the plasma, or projectiles not attached to the thruster.
In all of those references, and in U.S. Pat. No. 4,821,509, plasmas are produced in elongated tubes and are discharged from one end of the tube to provide propelling force on either a separate projectile or the thruster tube which is attached to the mass. The plasmas in these devices are produced by ablation of the walls of the tube or from liquid or semiliquid fuels by electrical discharges within the tube.
The references and U.S. Pat. No. 4,821,509 are useful for certain purposes. However there are continuing needs for higher efficiency thrusters and also for low power thrusters for station keeping and maneuvering of small satellites with limited electrical power resources. The present invention provides improved solutions to these needs.